The invention relates to a circuit arrangement for monitoring electrical isolation in a power supply system, in particular a motor vehicle, which electrical isolation is provided between a high-voltage system and a low-voltage system of the power supply system, wherein the high-voltage system and the low-voltage system are connected to ground, and wherein the high-voltage system has a first connection for a first supply voltage potential and a second connection for a second supply voltage potential of a voltage source.
In addition, the invention relates to a method for monitoring electrical isolation in a power supply system as has been described above.
Circuit arrangements and methods for monitoring electrical isolation are known from the prior art. In particular in the case of modern motor vehicles which have a so-called hybrid drive apparatus, the on-board power supply system comprises at least two subsystems, a high-voltage system which is connected to a high-voltage source, which supplies energy to at least one electric machine or draws energy produced by the electric machine, and a low-voltage source for supplying the conventional part of the on-board power supply system, which supplies energy to loads, for example, such as interior lighting, a radio or a navigation system. Standards, regulations and functional requirements demand electrical isolation between the high-voltage system and the low-voltage system. This electrical isolation needs to be monitored in order to be able to ensure safe operation of the motor vehicle. For this monitoring, various methods are already known, but these methods have the disadvantage that only asymmetric cases are identified, i.e. when the isolation or electrical isolation with respect to the two voltage systems are impaired identically, this cannot be identified. Other methods are complex and involve high costs, and further methods cannot be used in the case of a clocking inverter, i.e. they can only be implemented before or after an operating cycle, but not during use of the power supply system.
Generally, both voltage systems are connected to ground or to a ground connection, wherein the high-voltage system is expediently connected to ground at a high resistance, and to in each case one of the energy stores. For this purpose, the high-voltage system has two connections, of which one is or can be connected to a first supply voltage potential, for example the positive terminal, and the second connection is or can be connected to a second supply voltage potential, for example to the negative terminal, of the voltage source.